The present invention relates generally to optoelectronic communication systems and, more particularly, to an integrated optoelectronic module for parallel optical communication links.
There are many well-recognized benefits of using optical communication links to replace copper wiring in high data rate electronic systems such as computer systems, switching systems, and networking systems. Such potential benefits include increasing bandwidth and data rate, avoiding electromagnetic interference, limiting radiated electromagnetic noise from the system, reducing latency by placing optical/electrical (OLE) conversion as close as possible to the signal originating circuits (e.g., computer processors), increasing package density at lower cost per pin, among others.
At present, conventionally fabricated optoelectronic transducers typically include light emitting devices such as a Vertical Cavity Surface Emitting Laser (VCSEL) configured in a laser array, as well as light detecting devices such as photodiodes configured in a photodiode (PD) array. These optoelectronic transducers will often include an array of devices precisely arranged as a result of the scale and accuracy of photolithographic processes used to produce the individual semiconductors. That is, a series of VCSELS formed on a single wafer are cut or separated such that the array includes a desired number of optical emitters. These optoelectronic transducers include optical elements that are precisely arranged with the individual semiconductors to transmit and receive light.
Manufacturing lines for integrated circuits are inherently imperfect and invariably introduce defects into devices constructed on a wafer of semiconductor material. FIG. 1 illustrates a yield problem that results from six inoperable optical devices on a wafer 10 when it is desired to produce a 12-unit array. Each square on the surface 14 of the wafer 10 represents an instance of a semiconductor-based optical device. Devices marked with an “X” have a defect that renders the semiconductor device inoperable for its intended purpose. As a result of the defects, the desired number of elements in the array, and the fact that the wafer dicing process is performed by a rotating blade attached to a linearly translating carrier, only a limited number of such arrays can be produced from a single wafer.
In the example, devices marked in grayscale are individual members of a 12-device optical array that can be diced or separated from the wafer 10. Devices marked with a cross-hatch pattern are operable semiconductor devices that are discarded because they are not a member of a string of 12 contiguous semiconductor devices. FIG. 1 reveals that for the example wafer 10, relative device size, error rate and location, an error rate of less than 2% (or 6 inoperable devices out of 336 total devices on the wafer) results in a yield of 13 arrays (156 devices out of 336) for a yield rate of only 46.4%. Stated another way, about 51.8% of the operable devices on the wafer 10 are discarded (174 devices out of 336 total devices) because they are not in a row of 12 contiguous operable devices.
A need exists for an optoelectronic module that can be manufactured at relatively low costs with optical devices arranged in precise alignment with each other.